Key features are accurate rate control and uniform transverse distribution. Look for stable pressure regulation, calibrated flow metering, correct nozzle type and spacing, filtration strainers, recirculation that maintains uniformity without excessive shear, and a pump suited for emulsions. Tank design should prevent settling, with insulation if needed for temperature stability. The machine should support calibration procedures and provide distribution test capability. Practical factors include ease of cleaning, anti drip valves, corrosion resistant wetted parts, and compatibility with the viscosity and break speed of the specific emulsion grades you plan to spray.